Process of manufacturing



Patented Sept. 12, 1950 PROCESS OF MANUFACTURING PYRIDINECARBOXYLIC ACIDS Francis E. Cislak and William lnd., as Chemical Corporati dianapolis,

signers on,

corporation of Indiana No Drawing. Application March 25, 1942, Serial No. 438.168

21 Claims.

Our invention relates to a process of manuiacturing pyridinecarboxylic acids by the oxidaoline, and alkyl quinolines.

Heretofore pyrldinecarboxylic acids have been prepared by the oxidatio alkyl pyridines, quinoline, isoquinoline, or alkyl quinolines with potas- The preparation of pyrithis manner is costly and oxidation of the above-mentioned pyridine-ringcontaining compounds.

Fundamentally, our process consists in oxidizing the sulfates of the said pyridine-ring-containing compounds with nitric acid at elevated temperatures, with or without oxidation catalysts; if desired, with subsequent elimination of sulfuric acid.

The preferred manner in which our invention may be practiced is described trated, in the following examples.

Example 1.-In a one-liter flask, form a solution of 47 grams of 96% 3-picoline, cc. of concentrated sulfuric acid (96%), and 25 cc. of concentrated nitric acid Reflux this solution for about 2-3 hours; and then distill off the water formed by the oxidation (as well as the the nitric acid). and with it any remaining nitric acid. It is desirable to stop the distillation when the temperature of the liquid remaining in the flask reaches about 200 C.

Now cool the contents of the flask to about 0., and repeat the nitric-acid oxidation.

R. Wheeler, Into Reilly Tar & Indianapolis, [nd., a

( Cl. ZED-295.5)

2 To this end, add about 25 co. more concentrated nitric acid. Reflux the solution for about 23 hours. Distill oil the water, and the remaining nitric acid.

Repeat the procedure of the immediately preceding paragraph until a total of about 275 cc. of the concentrated nitric acid has been put through. When the last distillation has been completed, remove any remaining traces of nitric acid from the residue in the flask by aerating the hot solution.

Then cool the said residue about 700 cc. of water. a

If it is desired to eliminate sulfuric acid, add the calculated amount and dilute it with talline nicotinic acid in known manner.

Example 2.In place of intermittently adding small portions of nitric acid to the 3-picoline sulfate, refluxing, and distilling, as in Example 1,

the water and excess nitric acid. The entering nitric-acid vapor may be mixed with oxygen or air; in which case the amount of nitric acid required is diminished.

In a one-liter flask form a solution of 47 grams of 93% 3-picoline and 92 grams of 96% sulfuric acid. Heat this solution to a temperature of about -250 0., preferably about C., and maintain it at this temperature. Slowly (over a period of 15 to 25 hours) vaporize 300 aerate the hot solution to remove residual traces of nitric acid.

Cool and dilute the picoline-sulfate solution, and ii desired separate the nicotinic acid, as in Example 1.

Example 3.-In place of the 3-picoline of E use any of the other alkyl pyridines, such as Z-picoline. 4-picoline, 2,6- lutidlne, 2-ethyl pyridine. etc.. to obtain corresponding pyridinecarboxylic acids.

Example 4.-In place the a-picoline 01 Examples l and 2. we can use quinoline or isoquinoline, to obtain pyridinedicarboxyilc acids. or we can use alkyl quinolines to obtain pyridinedicarboxylic acids or alkyl pyridinedicarboxylic acids.

For instance, a solution of 64.5 g. of quinoline and 110 g. of 98% sulfuric acid is placed in any suitable vessel for bringing about intimate contact of as and liquid. and heated to 150-230" 0.. preferably about 180 0.: and the vapor of 500 to 800 cc. oi nitric acid is passed through over a period of 24-48 hours. The reaction mixture is cooled. and diluted with water, whereupon any small ouinolines precipitate and are filtered oil. The filtrate is made alkaline. and more lay-product nitro-cornpounds are precipitated and removed by filtration. The remaining alka ine solution contains a salt of quinolinic acid. 0n acidifying this alkaline so ution with acetic acid, and treating with a solution of co per sulfate. green copper ouinolinate is precipitated. From this copper salt ouinolinic acid may be pre ared by saturating its aqueous suspension with hydrogen sulfide. filtering of! the preci itated copper sulfide. and evaporating the filtrate until quinolinlc ac se arates.

if desired, we can use oxidation catalysts. such as vanadium or manganese sa ts. in anv of those Exam les 1 to 4. with ben ficial results: t ose catalysts are not necessary.

We claim as our invention:

1. The method of prod cing a ovridinecarhnxylic acid. which com rises oxidizing a su fate of a nvridine-rin -containin com ound 01 t e c ass consist ng of alkvl nvridines. ouinoi ne. iqnnuinoline. and aikvl ouinolines. with nitric acid at an elevat d t mperature suf iciently hi h to vannrize n tric acid and recovering the pyriinpr-orhoxvlic acid.

2.1he method of roducin a pvridinecarnszvlic acid as descri ed in claim 1. in which t e o ridine-ring-containing compound is 3- picoiine.

3. The method of producing a nvridinecarhnxviic acid as described in c aim 1. in which the pyrid ne-rine-cootaining com ound is ou noline.

4. The method of producing a nyridinecarhox l c ac d as de crihed in claim 1. in which the vrid ne-rin -rontaining compound is Z-nico ine.

5. The method of producin pvridinecarhoxylic acid as described in cla m 1. in which the ovridine-ring-containing compound is 4- n ol ne.

6. Th method of roducing pyridinecarhoazv c acid as described in claim 1. in which the o rid ne-ring-containing compound is an alkyl ou noline.

'1. The method of producing a pyridinecarboxvlic acid as described in claim 1, with the addition of the step of eliminating sulfuric acid.

8. The method of producing a pyridinecarboxylic acid. which comprises treating a pyridinering-containlne compound of the class consistmg of allryl pyridines, quinoline, isoquinoline. and alkvl quinolines. with sulfuric acid and nitric ac d at an elevated temperature willciently high to vaporize nitric acid and recoving the pyridinecarboxylic acid.

9. The method of producing a pyridinecar- 4 boxylic acid as described in claim 8, in which the pyridine-ring-containing compound is 3- picoline.

10. The method of producing a pyridinecarboxylic acid as described in claim 8, in which the pyridine-ring-containlng compound is quinoline.

11. The method of producing a pyridinecarboxylic acid as described in claim 8, in which the pyridine-ring-containing compound is z-picoline.

12. The method of producing a pyridinecarboxylic acid as described in claim 8, in which the pyridine-ring-containing compound is 4-picoline.

13. The method of producing a pyridinecarboxylic acid as in claim 6, with the addition 01. the step of eliminating sulfuric acid.

14. The method of producing a pyrldinecarboxylic acid which comprises oxidizing a sulfate of alkyl pyridine with nitric acid at elevated temperatures and recovering the pyridinecarboxylic acid.

15. The method of producing pyridinecarboxylic acids which comprises oxidizing a sulfate of the following compounds where R. is alkyl and the pyridine ring, temperatures and boxylic acid.

16. In the catalytic oxidation to a pyridinecarboxylic acid N-heteroaryl com ound grouping attached to the nitrogen-containing aromatic nucleus by one or more carbon-to-carbon linkages, the improvement which comprises conducting the oxidation by reacting nitric acid with the N-heteroaryi compound in the presence of a relatively small amount of the catalyst and suluric acid.

1'1. The process which comprises mixing sulfuric acid and a compound of the class consisting of alkyl pyridines and compounds having the structure with nitric acid at elevated recovering a pyrldinecarwhere R is selected from the group consisting of hydrogen and alkyl and N is the pyridine ring, and reacting the resultant mixture with nitric acid at elevated temperatures and recovering the so formed pyridinecarboxylic acid.

18. The process which comprises mixing sulturic acid and qulnoline, reacting the resultant mixture with nitric acid at elevated temperaturgs and recovering the so formed nicotinic aci 19. In the catalytic oxidation to a pyridinecarboxylic acid of an N-heteroaryl compound containing an oxidizable organic grouping attached to the nitrogen-containing aromatic nucleus by one or more carbon-to-carbon linkages. the improvement which comprises conducting the oxldation by adding nitric acid to a solution containing the N-heteroaryl compound and a relatively small amount of the catalyst dissolved in sulfuric acid.

20. m the catalytic oxidation to a pyridinecarboxyiic acid of an N-heteroaryl compound containing an oxidizable organic grouping attached to the nitrogen-containing aromatic nucleus by one or more carbon-to-carbon linkages, the improvement which comprises conducting the oxidation by reacting nitric acid with a sulfuric acid solution of the N-heteroaryl compound in the presence of a catalyst.

21. The method of producing a pyridinecarbosyiic acid as described in claim 8. in which the pyridine-flug-containing compound is an mm quinoline.

FRANCIS E- CISLAK. wnimam R. WHEELER.

tile of this patent:

Mater, "Das Pyridine und Seiner Derivatives," 

1. THE METHOD OF PRODUCING A PYRIDINECARBOXYLIC ACID, WHICH COMPRISES OXIDIZING A SULFATE OF A PYRIDINE-RING-CONTAINING COMPOUND OF THE CLASS CONSISTING OF ALKYL PYRIDINES, QUINOLINE, ISOQUINOLINE, AND ALKYL QUINOLINES, WITH NITRIC ACID AT AN ELEVATED TEMPERATURE SUFFICIENTLY HIGH TO VAPORIZE NITRIC ACID AND RECOVERING THE PYRIDINECARBOXYLIC ACID. 